Speech communication usually takes place in environments filled with competing sound sources and distorting environmental effects. Faced with such challenges, the peripheral and central auditory systems have developed a complex network of neural mechanisms that segregate and select auditory objects. Variability in individual listeners'abilities to perform spatial selective tasks may arise from a variety of differences in their abilities to use the cues available to the auditory system, and those individual differences may be exacerbated by reverberation and pathologies of the peripheral and central auditory systems. In the first aim of this project, individual differences in normal-hearing listeners'spatial selective auditory attention are measured using computer-simulated environments presented to subjects via headphones. In the second aim, threshold sensitivity to monaural and binaural temporal fine structure is measured for subjects in the top and bottom quartiles of the normal-hearing population. The relationship between performance on the spatial selective attention task and these simple measures is evaluated to see if differences in basic temporal processing predict differences on higher-order tasks. Studying, quantifying, and modeling how individuals use temporal auditory cues has important implications for assistive listening devices and speech recognition software, as well as for our understanding of the complex neural network that processes and modulates information provided by the senses. The third aim of this study will model the spatial selective attention data from Aim 1 by extending existing models of spatial processing, which use purely spatial information, to include effects of attention and selection. PUBLIC HEALTH RELEVANCE: Communication in complex settings with multiple, competing sources is often cited as difficult and frustrating for both hearing impaired and normal hearing listeners. This research will characterize the role played by fine time processing in spatial selective auditory attention in reverberant spaces, and it will model simple frameworks for combining bottom-up and top- down information to enable selective auditory attention. By identifying factors that explain some of the dramatic variability in the ability of normal-hearing listeners to successfully direct spatial selective attention, this research will move the field closer to effective signal processing schemas and development of assistive devices that will improve the quality of life of a large population of both hearing impaired and normal hearing individuals.